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Rola wodoru w procesie pękania spoin - nowe spojrzenie

100%

Tasak E. , Ziewiec A. , Adamiec J.

2008

tom R. 52, nr 5

138-138

Przeprowadzono analizę charakteru pękania spoin w stalach mikrostopowych, w stalach bainitycznych niskostopowych oraz w połączeniach różnoimiennych stali T91 z 10CrMo9-10. Ustalono, że wodór wywołuje również powstawanie pęknięć gorących w procesie krzepnięcia spoin. Przeprowadzone badania pozwoliły opracować mechanizm pękania spoin na gorąco oraz dalszego ich rozwoju jako pęknięć zimnych zwłocznych. Zweryfikowano również opisywany w literaturze mechanizm powstawania pęknięć typu "chewron" wykazując, że początkiem pęknięć zimnych typu "chewron" są pęknięcia gorące, w których "magazynowany" jest wodór wywołujący po ostudzeniu spoin pęknięcia zwłoczne.

It has been analysed the nature of weld metal cracking in micro-alloyed steels, bainitic low-alloy steels and in dissimilar joints of T91 with 10CrMo9-10 steels. It has been found that hydrogen induces also hot cracking during the weld solidification process. The authors' investigations enabled to develop the weld metal hot cracking mechanism as well as that of their further growth as delayed cold fractures. The mechanism of chewron type cracking described in the scientific literature has been also verified, pointing out that the chewron type cracks are initiated from hot cracks in which hydrogen is "stored" and induces the delayed fractures after cooling down the welds.

Carbonation cracking of reinforced AAC panel

80%

Matsushita F. , Aono Y. , Shibata S.

2011

tom nr spec.

81-85

Carbonation cracking and its mechanism of AAC have not been reported at all. One of the possible mechanisms of carbonation cracking caused by carbonation shrinkage is investigated. Carbonation shrinkage at the occurrence of cracking was approximately 0.12% both for field study and accelerated carbonation, while carbonation degree was approximately 50% and 35%, respectively. Tensile stress in AAC was calculated to reach tensile strain capacity (0.04-0.05%) at the occurrence of cracking both for field study and accelerated carbonation data. In other words, the proposed mechanism of carbonation cracking was certified.

Mechanical properties dependency of the pearlite content of ductile irons

80%

Gonzaga R. A. , Martinez Landa P. , Perez A. , Villaneuva P.

2009

tom Vol. 33, nr 2

150-158

Purpose: In this work, it is pretended to make a comparison of different pearlite contents in pieces with similar shape and dimensions and to analyze the variation of mechanical properties as pearlite content increases. The three pieces used had form of stair made of ductile cast iron. Design/methodology/approach: The present study was based on an adequate balance of alloying elements. None heat treatment was used to obtain different pearlite contents in the microstructures. Many specimens taken from the cast were mechanized to be polished and swabbed with nital to analyze the microstructure. To study the mechanical properties these casts present many tests were done such as Charpy impact test, done at different temperatures. Fracture toughness and tensile strength tests were done, as well. Findings: This study gave evidences that heat treatments are not necessary to obtain different pearlite content in the microstructure. Good mechanical properties are obtained by an appropriate balance of alloying elements. Research limitations/implications: They are that of natural sources. Besides, high and precision technology must be applied to get the present results better. Practical implications: Cast iron productions are focussed straight on machine building and automotive industries and constructions. The low cost production of ductile cast iron, its mechanical properties and low cost transformations are the tempting for application. Originality/value: The whole experimental work and the appropriate results obtained as consequences of the analysis carried out are novel, although applied methods are well known. Values presented in tables are given as new results of our experiments. This work is of great importance for the development of new economical methods for ductile iron production. This study is directed to researchers and metallurgy centres.